1. Field
The inventive concept relates to an interference cancellation repeater, and more particularly, to an interference cancellation repeater capable of stable operation irrespective of characteristics of a radio signal.
2. Description of the Related Art
In a mobile communication system, a repeater performs intermediate amplification between a base station and a mobile station (mobile communication terminal) and extends coverage of the corresponding base station when a propagation environment is poor and a distance from the base station is long. The repeater filters and amplifies signals by frequency band to provide mobile communication services to areas blocked or isolated from the outside.
Frequencies of radio signals transmitted/received by the repeater are identical, so that some of the signals output through the repeater may be re-input to the repeater directly or reflectedly through a space in a form of a feedback signal. The feedback signal is amplified by being combined with an original signal received from the base station or the mobile communication terminal, and then output through the repeater. When the above processes are repeated, the repeater oscillates.
In order to prevent such a phenomenon, an interference cancellation system (ICS) capable of canceling the feedback signal is being developed. Generally, the ICS includes an amplifier to perform a signal amplification function. The amplifier amplifies signals according to a predetermined amplification gain, but if the amplification gain is not properly set, the ICS may oscillate.
In particular, in a case of an ICS repeating a long term evolution (LTE) signal, a proper amplification gain may not be obtained due to a severe power level change over time. Therefore, there is a need for a method capable of setting an appropriate amplification gain so as to operate the ICS more stably.